1. Technical Field
The present invention relates to an electric power conversion circuit system, and in particular, to an electric power conversion circuit system having a plurality of input/output ports.
2. Related Art
JP 2012-125040 A proposes an electric power conversion circuit system in which two types of circuits are integrated, taking advantage of magnetically coupled reactors showing different inductances in the current directions. The system has a structure in which coupled reactors are placed on both ends of a transformer, and are connected to full-bridge circuits. In this structure, a maximum of four direct current ports are provided in one circuit. When electric power is transmitted between the left and right full-bridge circuits connected on the respective ends of the transformer, if the duty ratios (Duty) are the same, high-efficiency electric power transmission is possible.
As described above, the electric power can be transmitted with high efficiency from one full-bridge circuit to the other if the duty ratios of the left and right full-bridge circuits are the same. However, when the duty ratios differ from each other, a current during a non-transmission period is increased, and the conversion efficiency is significantly reduced. Therefore, there is a restriction to set equal duty ratios between the left and right full-bridge circuits, which means that the voltage value of the direct current port connected to the intermediate point of the transformer cannot be arbitrarily selected.
In view of the above, the present inventors have proposed controlling a half-bridge phase difference between half-bridge circuits forming the full-bridge circuit, so that the reduction of the conversion efficiency can be inhibited even when the duty ratios differ between the full-bridge circuits. However, in this related art that was proposed (not yet made public at the time of filing of the present application) also, the advantages may be insufficient, and a further improvement in efficiency is desired. In particular, there is a problem in that the efficiency may be reduced when there is a dead-time period or when the power supply voltage changes.
The present invention advantageously provides an electric power conversion circuit system having a plurality of input/output ports, that can transfer the electric power with high efficiency even during a dead-time period or even when the power supply voltage changes.